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Abstract: The objective of this review is to make the field of “flame retardants for polymer materials” more accessible to the materials science community, i.e. chemists, physicists and engineers. We present the fundamentals of polymer combustion theory, the main flame retardant properties and tests used to describe fire behavior, together with the nature and modes of action of the most representative flame retardants and the synergistic effects that can be achieved by combining them. We particularly focus on polymer nanocomposites, i.e. polymer matrices filled with specific, finely dispersed nanofillers, which will undoubtedly pave the way for future materials combining physicochemical and thermo-mechanical performances with enhanced flame retardant behavior. [Copyright &y& Elsevier]

The use of a nonreactive thermoplastic (TP) that is initially miscible and which phase separates during reaction has often been used to improve the toughness of epoxy networks. Most of the time no real improvement in fracture properties is obtained due to poor adhesion between phases. In this work the grafting of amino groups on the backbone of a polyetherimide (PEI) is studied. In order to avoid too high a degree of grafting and crosslinking of PEI, a synthesis in a dispersed medium is considered. Three amines are used: ethylene diamine (EDA), 1-2 aminoethyl-piperazine (AEP) and n-butylamine. The grafting reaction was characterized by FTIR, SEC and NMR. The influence of the drying and washing processes of the powder is shown. The degree of grafting is determined using both titration and nitrogen microanalysis and is in the range 1–5%. The glass transition temperatures of the amino grafted PEI decrease, almost linearly with the degree of grafting. [Copyright &y& Elsevier]

The flame retardant effect of hydrated lime, partially and completely hydrated dolomitic limes in polyethylene and ethylene vinyl acetate copolymers was evaluated and compared to that of magnesium hydroxide and aluminium hydroxide. An important decrease of the peak of heat release rate as measured by cone calorimeter test was observed for Ca-based composites. Thermogravimetric and X-Ray Diffraction analysis indicated that the calcium hydroxide fraction plays an important role in the generation of an intumescent mineral residue during the combustion. [ABSTRACT FROM AUTHOR]

The engrailed gene is a transcription factor required in numerous species for major developmental steps (neurogenesis, limb development, boundary establishment), and its evolution is known to be closely related to the evolution of the metazoan body plan. Cephalopods exhibit numerous morphological peculiarities among molluscs, such as a direct development, a complex sensory and nervous system (eyes, brain, giant axons), a reduced shell, a funnel, and a brachial crown. We assessed a potential recruitment of engrailed in the development of these derived traits and examined the expression pattern of engrailed during the organogenesis of the cuttlefish Sepia officinalis, by immunostaining. Engrailed was detected at the margin of the prospective internal shell, which is consistent with studies on molluscs having an external shell and confirms a conserved role of engrailed in delimitating the molluscan shell compartment. Interestingly, unexpected patterns were early detected in the emerging arms, funnel and optic vesicles and latter in tentacles and eye lids. We also identified an engrailed cognate in the squid Loligo, which provides new evidence that engrailed in molluscs is not restricted to a ‘shell function’ and has been recruited in the mollusc lineage for the emergence of morphological novelties in cephalopods. [ABSTRACT FROM AUTHOR]

Surface morphology and bulk structure of polylactide (PLA) modified with halloysite nanotubes (HNT) treated with N,N'-ethylenebis(stearamide) (EBS) and untreated, as well as reference materials - PLA, EBS, and a blend of PLA with EBS, were examined. HNT is known to improve PLA properties, including mechanical and barrier properties. The materials were cold crystallized and tested using DSC, TGA, PLM, SALS, SEM, AFM. The additives affected nucleation and crystallization of PLA, but did not influence crystallinity, which was of approx. 37-40%. In bulk, PLA crystallized in the form of spherulites in all materials. However, on surfaces of EBS-containing materials, a thin EBS layer with domain morphology was found. The EBS layer induced epitaxial crystallization of PLA in the form of parallel stacks of edge-on lamellae, the phenomenon reported for this polymer pair for the first time. It was observed in PLA with EBS modified HNT and in the PLA blend with EBS. Moreover, the EBS layers imparted hydrophobicity to the EBS-containing materials. [ABSTRACT FROM AUTHOR]

The effect of hygrothermal aging on the mechanical behaviour of polyamide 6 (PA6) material filled with 10 wt % multi-walled carbon nanotubes (MWCNTs) has been investigated experimentally. Young’s modulus and flexural modulus of the materials are decreased by more than 30% for the conditions of 25°C/85% RH, compared to the reference conditions of 25°C/55% RH (RT), while the flexural strength by 6–17%. The decrease is larger for the conditions of 40°C/85% RH, which reveals that the effect of combined elevated temperature and moisture is more severe. The decrease in the properties is smaller for the MWCNT/PA6 specimens, which shows that the presence of MWCNTs mitigates the effect of hygrothermal aging. Finally, it is observed that the increase in the properties of the MWCNT/PA6 material is so large, for the specific MWCNT concentration, that it compensates the negative effect of hygrothermal aging. [ABSTRACT FROM PUBLISHER]

Bio- and CO2-sourced non-isocyanate polyurethane (NIPU) microcellular foams were prepared using supercritical carbon dioxide (scCO2) foaming technology. These low-density foams offer low thermal conductivity and have an impressive potential for use in insulating materials. They constitute attractive alternatives to conventional polyurethane foams. We investigated CO2's ability to synthesize the cyclic carbonates that are used in the preparation of NIPU by melt step-growth polymerization with a bio-sourced amino-telechelic oligoamide and for NIPU foaming. Our study shows that CO2 is not only sequestered in the material for long-term application, but is also valorized as a blowing agent in the production of NIPU foams. Such foams will contribute to energy conservation and savings by reducing CO2 emissions. [ABSTRACT FROM AUTHOR]

Fully bio- and CO2-sourced non-isocyanate polyurethanes (NIPUs) were synthesized by reaction of carbonated soybean oil (CSBO) either with biobased short diamines or amino-telechelic oligoamides derived from fatty acids to achieve respectively thermoset or thermoplastic NIPUs. Biobased carbonated vegetable oils were first obtained by metal-free coupling reactions of CO2 with epoxidized soybean oils under supercritical conditions (120 °C, 100 bar) before complete characterization by FTIR, 1H NMR, and electrospray ionization mass spectroscopy (ESI-MS). In a second step, biobased NIPUs were produced by melt-blending of the so-produced cyclocarbonated oil with the biobased aminated derivatives. The thermal and mechanical properties of resulting polymers were found to be depending on the cyclocarbonated vegetable oil/amine ratio. More precisely, short diamines and CSBO led to the formation of cross-linked NIPUs, and the resulting tensile and thermal properties were poor. In contrast, elastomeric NIPUs derived from oligoamides and CSBO exhibited a better rigidity, an improved elongation at break (εr up to 400%), and a higher thermal stability (T95-wt-% > 350 °C) than those of starting oligoamides. These results are impressive and highlight the potentiality of this environmental friendly approach to prepare renewable NIPU materials of high performances. [ABSTRACT FROM AUTHOR]

Abstract: Immiscible blends of 80 wt% polypropylene (PP) with 20 wt% polyamide (PA) or polycarbonate (PC) were prepared by melt mixing with or without the addition of 5% nanosilica. The nanosilica produced a strong reduction of the disperse phase droplet size, because of its preferential placement at the interface, as demonstrated by TEM. Polarized Light Optical Microscopy (PLOM) showed that adding PA, PC or combinations of PA–SiO2 or PC–SiO2 affected the nucleation density of PP. PA droplets can nucleate PP under isothermal conditions producing a higher nucleation density than the addition of PC or PC–SiO2. PLOM was found to be more sensitive to determine differences in nucleation than non-isothermal DSC. PP developed spherulites, whose growth was unaffected by blending, while its overall isothermal crystallization kinetics was strongly influenced by nucleation effects caused by blending. Addition of nanosilica resulted in an enhancement of the strain at break of PP–PC blends whereas it was observed to weaken PP–PA blends. [Copyright &y& Elsevier]

Summary: The influence of the incorporation of hydrophobic nanosilica on morphological and mechanical properties of polyamide 6 (PA) and poly(propylene) (PP) blends has been investigated. Depending on the amount of silica nanoparticles in the blend and the melt mixing procedure, a strong refinement of PP (as minor dispersed phase) droplet size can be achieved thanks to the interfacial confinement of nanoparticles. The accumulation of nanoparticles at the interface allows the formation of an anti-coalescence rigid barrier around PP domains that prevents/refrains dispersed phase domains from coalescence as highlighted by transmission and scanning electron microscopies. The mechanical properties of the hybrid blends were also discussed and interpreted in relation with the blend morphology. [ABSTRACT FROM AUTHOR]